C.S. Lewis, the famous Anglican writer, once wrote: "The very possibility of progress demands that there should be an unchanging element ...the positive historical statements made by Christianity have the power ...of receiving, without intrinsic change, the increasing complexity of meaning which increasing knowledge puts into them" ("God in the Dock," Eerdmans, Grand Rapids, MI, 1970, 44-47). Doctrine clearly develops within Scripture ("progressive revelation"). Examples: doctrines of the afterlife, the Trinity, the Messiah (eventually revealed as God the Son), the Holy Spirit (Divine Person in the New Testament), the equality of Jews and Gentiles, bodily resurrection, sacrifice of lambs evolving into the sacrifice of Christ, etc. This book serves as an introduction to the notion of doctrinal development, written from a popular lay apologetics standpoint.